The present invention is directed to a composition and a method for forming amidoamines and polyamides from polyalkylene polyamines. More specifically, the present invention is directed to amidoamine curing agent compositions formed from polyalkylene polyamines and epoxy-amine compositions.
Polyamide and amidoamine epoxy curing agents are utilized extensively in many markets including protective metal and concrete coatings, adhesives and sealants, composites, and electrical encapsulation. Polyamide epoxy curing agents comprise the reaction products of dimerized fatty acids (dimer fatty acid) or esters and polyethylene polyamines, and usually a certain amount of monomeric fatty acid, which helps to control molecular weight and viscosity. “Dimerized” or “dimer” or “polymerized” fatty acid refers, in a general way, to polymerized fatty acids obtained from unsaturated fatty acids.
Dimer fatty acid is usually prepared by the acid-catalyzed oligomerization of monomeric unsaturated fatty acids under pressure probably by a Diels Alder mechanism. Usually tall oil fatty acid (TOFA) is used, although other plant fatty acids occurring in natural oils, such as soya oil, linseed oil, tung oil, perilla oil, oiticica oil, cornseed oil, sunflower oil, safflower oil, dehydrated castor oil, and the like, can be used as well. Commercial products of dimer fatty acids generally consist of mostly (>70%) dimeric species, with the rest consisting mostly of trimers and higher oligomers, along with small amounts (generally less than 5%) of monomeric fatty acids. Common monofunctional unsaturated C16 to C22 fatty acids also employed with the dimer fatty acids in making polyamides include tall oil fatty acid (TOFA), soya oil, linseed oil, cottonseed oil, or the like.
Amidoamine epoxy curing agents comprise the reaction products of monofunctional higher fatty acids or esters and polyethylene polyamines. The monofunctional higher fatty acids represent both saturated fatty acids, and unsaturated fatty acids with one or more double bonds. Examples of monofunctional unsaturated fatty acids occurring in natural oils, such as linseed oil, tall oil (tall oil fatty acid (TOFA)) and dehydrated castor oil, are a mixture of 9,11-octadecadienic acid (2 double bonds), 9,12-octadecadienic acid (2 double bonds), oleic acid (1 double bond), linoleic acid (2 double bonds), linolenic (3 double bonds), alpha-eleostearic acid (3 double bonds) and beta-eleostearic acid (3 double bonds). Examples of saturated fatty acid occurring in natural oils include lauric acid (C12), myristic (C14), palmitic acid (C16), and steric acid (C18). Appropriate synthetic fatty acids can also serve as starting material for amidoamine curing agents. The fatty acid can be used individually or as a mixture of more than one fatty acid. Commonly used fatty acids for amidoamines include tall oil fatty acid (TOFA), soya oil, linseed oil, cottonseed oil, or the like. Small amounts of dimer acid can also be incorporated into amidoamine synthesis.
The polyethylene polyamines, such as diethylene triamine (DETA), triethylene tetramine (TETA), tetraethylene pentamine (TEPA), pentaethylene hexamine (PEHA), hexaethylene heptamine (HEHA), and the like, are employed in the preparation of polyamide and amidoamine curing agents. In actual commercial practice, the polyethylene polyamine most commonly employed in polyamide preparation is TETA and TEPA in amidoamine synthesis.
In addition, other monofunctional or difunctional carboxylic acids, or other multifunctional polyamines, may be incorporated into the condensation process in order to provide specialized property enhancements for polyamide and amidoamine curing agents.
Polyethylene polyamines are conventionally manufactured from the reaction of ammonia with either ethylene dichloride or ethanolamine. As new manufacturing assets are built to produce polyethylene polyamines, there is a tendency to favor the ethanolamine process, as it is less corrosive to the manufacturing equipment, and hence, more economical. Unfortunately, the ethanolamine process generally produces a lower yield of higher polyethylene polyamines, such as TETA and TEPA, than the ethylene dichloride process, and therefore prices for TETA and TEPA are increasing relative to the prices for other polyethylene polyamines. Furthermore, the demand for higher polyethylene polyamines, especially TEPA, is increasing. There is therefore a need for more economical alternatives to TETA, and especially TEPA, in the manufacture of polyamide and amidoamine curing agents.
Several methods for preparation of polyamide and amidoamine and their use as epoxy curing agents are known. For example, U.S. Pat. No. 2,705,223 describes epoxy resins cured with polyamides based on polymeric fatty acids and polyethyleneamines.
GB 2,031,431 discloses epoxy resins cured with mixtures of high molecular weight polyoxyalkylene polyamines and N,N′-bis(3-aminopropyl)ethylenediamine.
U.S. Pat. No. 4,463,157 discloses self-curing, amide-group-containing aminourea resins produced from a polyaminoamide, which has been produced from polyalkylene-polyamines reacted with fatty acids and/or from polyalkylene-polyamines reacted with dimer fatty acids. Table 1 of U.S. Pat. No. 4,463,157 shows the product of reaction of N,N′-bis(3-aminopropyl)ethylenediamine with ricinene fatty acid.
U.S. Pat. No. 8,293,863 discloses polyamide curing agent compositions, including the reaction products of (1) multifunctional amines of the following structure:
wherein R1 is CH2CH2CH2NH2; R2, R3 and R4 independently are H or CH2CH2CH2NH2, and X is CH2CH2 or CH2CH2CH2, with (2) dimer fatty acids, optionally in combination with monofunctional fatty acids. The reaction product may include at least 15 wt % tetrahydropyrimidine-containing components.
The disclosure of the foregoing publications, including patents and patent applications, is hereby incorporated by reference.